In a telephone interview with the Guardian, Liu Xia said police officers had surrounded her home and warned her that she could not leave without a minder.

"They have told me not to go out, not to visit friends. If I want to see my parents or buy food, I can only go in their car," she said. "I don't even talk to my neighbours because I don't want to get them into trouble."

During a prison visit on Sunday, Liu Xiaobo asked her to collect the prize at the ceremony in Oslo, Norway, on 10 December. But she was doubtful she would get as far as the airport.

"I can't even get out of my home, how could I go out of the country?"

The Nobel prize committee said they hoped one of the couple would attend the ceremony, but it would go ahead without the winner as it did for Burmese democracy leader Aung San Suu Kyi and former Polish president Lech Walesa.

The Chinese government today maintained its attack on the Nobel decision and its supporters. ""If some people try to change China's political system in this way, and try to stop the Chinese people from moving forward, that is obviously making a mistake," said the foreign ministry spokesman Ma Zhaoxu told the Associated Press. "This is not only disrespect for China's judicial system, but also puts a big question mark on their true intentions."

Asked whether Liu Xiaobo would be allowed to collect the award Dec. 10 in Oslo, Ma would only respond by saying that it is "up to judicial authorities." He avoided saying whether Liu's wife would be allowed to go.

He also refused to answer questions about Liu Xia's treatment, even saying at first that he did not know who she was.

Liu Xiaobo, a literature professor, was commended by the Nobel committee for his peaceful advocacy of increased political rights and civil liberty in China over a period of more than 20 years.

But domestic newspapers claimed the award to Liu, who co-authored the Charter 08 campaign for reform, is part of a plot to destabilise China. Police have detained or warned at least 30 of his friends, many of whom gathered to celebrate the announcement.

The Nobel committee said China's accusations of interference were as misguided as its response.

"We regret the actions they have taken, but I have to say we are not surprised," said Geir Lundestad, secretary of the committee. "We stand for a set of principles. A committee can't just overthrow a government. That is self-evident. We have no such power or intention. We are just five independent members. We take instructions from nobody."